Uveitis is a major cause of blindness in the United States. Pars planitis is a well-defined disease subset of uveitis. The causes of pars planitis, as well as other uveitis subsets, are frequently unknown. The overall objective of this project is to characterize a distinctive protein, called P-36, which we have identified in the plasma/serum of pars planitis patients during acute exacerbation of the disease, and to investigate its possible role in the pathogenesis of pars planitis. The identification of a protein which may contribute to the pathogenesis of pars planitis would be a major advance toward its treatment and possible cure. We propose the following specific aims: A. To identify P-36 in the plasma/serum of pars planitis patients, to quantitate its levels in patient's plasma/serum, to correlate P-36 levels with disease activity, and to determine whether it circulates freely or as a part of a larger molecular complex. B. To identity and characterize P-36 in the eye. C. To identity a potential biological function for P-36. Quantitative assessment of P-36 levels in patients' plasma/serum may be of value in both monitoring disease activity and guiding treatment. The proposed study would provide the precise structural information about the protein. Studies involving functional properties of P-36 will help us in understanding the mechanism of ocular inflammation in pars planitis and possibly to design more effective treatment for this disease.